MNL20-2ND

Chapter 12-Seawater

As IN OTHER NATURAL environments, corrosion testing in seawater is dependent upon the actual environmental conditions experienced by the exposed materials during the entire duration of exposure. These environmental conditions can vary widely in any specific location. Normal seasonal variations as well as variations from year to year and temporary natural or manmade conditions can dramatically affect the conditions of exposure that control overall corrosion behavior of materials. Seasonal variations include changes in temperature, dissolved oxygen content, and the type and extent oi biological fouling. Significant year-to-year variations such as those caused by the aperiodic general ocean surface water warming in the eastern Pacific Ocean, called El Niño, also affect the seawater environment over a wide area. Temporary natural conditions may include natural proliferation of microorganisms such as the “red tide” blooms of algae that can significantly reduce dissolved oxygen availability. Temporary manmade conditions such as spills of oil, chemicals, and sewage can also have a dramatic effect on the local environment that can affect corrosion.